Featured Research

from universities, journals, and other organizations

New Map Of Daily Probability Of Earthquake Shaking In California

Date:

June 21, 2005

Source:

U.S. Geological Survey

Summary:

The U.S. Geological Survey (USGS) has announced the release of new public web pages that show the probability of earthquake shaking in the next 24 hours in California. These maps graphically illustrate the change in earthquake probability during aftershock and possible foreshock sequences.

Share This

This is an example of a time-dependent map giving the probability of strong shaking at any location in California within a 24-hour period. For this purpose, 'strong shaking' is defined as Modified Mercalli Intensity (MMI) VI, or the level of shaking that throws objects off shelves.

The U.S. Geological Survey (USGS) has announced the release of new public web pages that show the probability of earthquake shaking in the next 24 hours in California. These maps graphically illustrate the change in earthquake probability during aftershock and possible foreshock sequences.

Related Articles

The maps are not intended to be used to predict an upcoming earthquake; however, based on previous earthquake sequences, an increase in probability will be seen before about half of California's larger earthquakes. The maps are updated at least once an hour and are available to the public at http://pasadena.wr.usgs.gov/step/.

"The new maps represent a synthesis of our knowledge about earthquakes in California," said Dr Lucy Jones, Scientist-in-charge of the USGS Earthquake Hazards Program in Southern California. "They factor in our knowledge of faults, underlying geology and expected rates of earthquake aftershocks."

The new maps and the way they were developed are discussed in an article in the current issue of the journal Nature. The methodology was developed by a team from the Swiss Federal Institute of Technology (ETH) in Zurich, Switzerland, and the U. S. Geological Survey in California, with funding from the Southern California Earthquake Center, ETH and the USGS.

In almost all cases, said Jones, the probabilities on this map will be very low. The background probability for strong to moderate earthquake shaking in most of California is between 1-in-10,000 and 1-in-100,000. By comparison, the average American's risk of being in a car accident in any 24-hour period is 1-in-2,500. "The only time that probabilities become large enough to cause concern is after a significant earthquake that may have already caused damage," explained USGS seismologist Dr Matt Gerstenberger. "Aftershocks are likely in this situation, and the new maps show where those aftershocks are most likely to be felt and how the hazard changes with time."

In the system used to create the maps, the probability of strong earthquake shaking (with a Modified Mercalli Intensity of VI or greater) in the next 24 hours is calculated, based upon the known behavior of aftershocks and the possible shaking pattern predicted from historical patterns on the fault or in the area. The system considers all earthquakes, large and small, that are recorded by the California Integrated Seismic Network (CISN), the California element of the Advanced National Seismic System (http://pasadena.wr.usgs.gov/recenteqs/). These probabilities apply both to aftershocks smaller than the first event and to the possibility that the "aftershock" will, in fact, be larger than the first event -- in which case it becomes a "foreshock."

Seismologists have known for decades that the occurrence of one earthquake makes another event more likely. The probability of one earthquake triggering another has been quantified and depends on magnitude, distance and time from the triggering event. These relationships have been used to issue statements about possible aftershocks after significant earthquakes in California for the last 15 years.The innovations in the map include information about the spatial distribution of aftershocks, how the shaking varies by location and how the probability of earthquakes varies with time.

The results of these calculations have been statistically verified against the catalog of Californian earthquakes from 1988 to 2002, said Jones. The testing showed that these maps do a significantly better job statistically of predicting the occurrence of earthquakes in California than long-term hazard maps alone or long-term hazard maps with generic aftershock probabilities. Because this has been statistically verified, the new maps can also now function as a "null hypothesis" for other claims of earthquake prediction.

This product has been reviewed by the California Earthquake Prediction Evaluation Council, which determined that this methodology represents the state of the art in evaluation and illustration of aftershock probabilities. Implementation of these maps for other areas outside California depends upon both a robust real-time seismic network and the research to establish the average rate of aftershocks for that area, Jones said.

U.S. Geological Survey. (2005, June 21). New Map Of Daily Probability Of Earthquake Shaking In California. ScienceDaily. Retrieved March 31, 2015 from www.sciencedaily.com/releases/2005/06/050619195036.htm

More From ScienceDaily

More Earth & Climate News

Featured Research

Mar. 31, 2015 — The ocean is a large reservoir of dissolved organic molecules, and many of these molecules are stable against microbial utilization for hundreds to thousands of years. They contain a similar amount ... full story

Mar. 31, 2015 — Using the assessment tool ForWarn, US Forest Service researchers can monitor the growth and development of vegetation that signals winter's end and the awakening of a new growing season. Now these ... full story

Mar. 31, 2015 — Geoscientists have revealed information about how continents were generated on Earth more than 2.5 billion years ago -- and how those processes have continued within the last 70 million years to ... full story

Mar. 31, 2015 — Until now electric fences and trenches have proved to be the most effective way of protecting farms and villages from night time raids by hungry elephants. But researchers think they may have come up ... full story

Mar. 31, 2015 — Researchers have detected a human fingerprint deep in the Borneo rainforest in Southeast Asia. Cold winds blowing from the north carry industrial pollutants from East Asia to the equator, with ... full story

Mar. 31, 2015 — Landfills can make a profit from all their rotting waste and a new patent explains exactly how to make the most out of the stinky garbage sites. Decomposing trash produces methane, a landfill gas ... full story

Mar. 31, 2015 — As the five-year anniversary of the explosion of the Deepwater Horizon oil rig approaches, a new report looks at how twenty species of wildlife are faring in the aftermath of the ... full story

Mar. 31, 2015 — Scientists have discovered why the first buds of spring come increasingly earlier as the climate changes. As the climate changes the sweet spot for seeds comes earlier in the year, so first flowers ... full story

Mar. 31, 2015 — In the 1990s the discovery of the oldest human made and completely preserved wooden hunting weapons made the Paleolithic excavation site in Schoningen internationally renowned. Contained within the ... full story

Mar. 31, 2015 — The adverse health effects caused by fine particles have been known for some time. In addition, ultrafine particles appear to play a significant role in cardiac function -- even if an individual is ... full story

Related Stories

Mar. 10, 2015 — A new California earthquake forecast by the U.S. Geological Survey and partners revises scientific estimates for the chances of having large earthquakes over the next several ... full story

Aug. 24, 2011 — A magnitude-5.3 earthquake rattled southern Colorado Monday, August 22, at 11:46 p.m. MDT, causing strong shaking, but minor damage, and was felt throughout the state of Colorado and neighboring ... full story

Aug. 24, 2011 — A magnitude 5.8 earthquake struck the National Capital Area on Tuesday, August 23, at 1:51p.m. (EDT), causing moderate shaking and potentially significant damage, and was felt throughout Northern ... full story

Mar. 15, 2011 — The U.S. Geological Survey has updated the magnitude of the March 11, 2011, Tohoku earthquake in northern Honshu, Japan, to 9.0 from the previous estimate of 8.9. Independently, Japanese ... full story

ScienceDaily features breaking news and videos about the latest discoveries in health, technology, the environment, and more -- from major news services and leading universities, scientific journals, and research organizations.